The standard devices in the field of measurement of rheological properties of concrete are described by GH Tattersall and PFG Banfill ("Tattersall"), in chapter 6 of their treatise, The Rheology of Fresh Concrete (Pitman Publishing Inc. 1983). The various devices described, all involve the mixing of the concrete in a bowl by either concentric or planetarily movable paddles, driven through an electric motor with an hydraulic transmission. Mixing torque, with correlation to concrete viscosity and other rheological properties of the concrete, is determined by variations in oil pressure in the hydraulic gear box, occasioned by the torque of mixing.
While such devices provide some measurement of the rheological properties of concrete, there are inherent properties of the system which result in substantial measuring errors. Since the mixing torque is measured by monitoring oil pressure in the hydraulic gearbox there is no allowance for energy losses in the drive system between the hydraulic gearbox and the mixing paddle. In addition, there is no provision for oil temperature corrections which cause pressure and measurement deviations.
In addition, while the Tattersall device provides some degree of accuracy with concrete, its indirect torque measurements are not suitable for accurate measurement of the rheological properties of high density mill tailings, which have completely different "aggregate" gradations, and different water to solids ratios by an order of magnitude. The tailings also interact chemically with the binder system, with deviations resulting from different products and their rheological properties, as well as diminution of reactant materials.